In the end, Boston bombing suspect is done in by a flapping tarp

JUST WATCHED

Duffy: My stepfather is a real hero

MUST WATCH

Story highlights

Suspect Dzhokar Tsarnaev hides in a covered boat in a Watertown backyard

Boat owner David Henneberry notices a section of loose tarp

One of the bindings has been cut

Henneberry sees a pool of blood in the boat and calls 911

Something didn't look right.

David Henneberry had been cooped up for hours, stuck inside as police searched for a suspect in the Boston Marathon bombings. He ventured out for some fresh air after police lifted their order to stay indoors.

He looked at the boat parked in his yard.

What he saw brought an end to the authorities' sweeping manhunt. It would lead them to a fugitive, who was hiding on the floor of his boat.

"The tarp on his winterized boat had sort of been flapping in the wind," his stepson Robert Duffy told CNN's Piers Morgan.

Henneberry had tied down the covering on the vessel in his backyard so firmly that it had not budged all winter long, not even through this year's blizzards.

"He got closer and realized that one of the retention straps had literally been cut -- not chafed, not broken or unhooked," Duffy said. Henneberry saw something else -- something on the tarp that looked like blood.

The Watertown resident thought some animal had forced its way into his boat. Maybe it was a squirrel, he told his stepson.

Henneberry's call to police put an end to the hunt for the man suspected of planting one of two bombs that exploded near the finish line of the Boston Marathon, killing three and inflicting injuries on dozens more that are typical of wounds sustained in conflict regions such as Afghanistan and Iraq.

Before police stopped him, Dzhokar Tsarnaev, with his older brother, Tamerlan, allegedly shot a university policeman dead, hijacked a car at gunpoint, then fired upon and threw grenades at officers pursuing them.

Police shot and killed the brother, but Dzhokar Tsarnaev eluded them all day Friday -- until Henneberry's 911 call.

Before opening fire, authorities, using a bullhorn, called on the younger Tsarnaev to surrender.

A standoff followed. When it finally ended and police approached the boat, they were aware of the danger the armed man posed.

Unlike Henneberry, they used a robot to pull back the tarp over the boat.